Air compressor having improved valve device

ABSTRACT

An air compressor includes a cylinder housing, a piston moved to slide in the cylinder housing in a reciprocating action to generate pressurized air, and a sealing ring engaged into the piston and having an outer peripheral channel formed in an upper portion to form an outer peripheral rib, the outer peripheral rib of the sealing ring is extended out of the piston for slidably engaging with the inner peripheral surface of the cylinder housing and for making an air tight seal between the cylinder housing and the piston even when the piston is tilted relative to the cylinder housing. The sealing ring is retained between a base member and an upper cover member of the piston.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an air compressor, and more particularly to an air compressor having an improved valve device for facilitating a sliding engagement between a piston and a cylinder housing and for effectively controlling air to flow through the valve device or to flow into and out of the cylinder housing.

2. Description of the Prior Art

Typical air compressors comprise a cylinder housing attached or secured to a base and having a piston slidably disposed therein, and a motor secured to the base and coupled to the piston of the cylinder housing for actuating or driving the piston of the cylinder housing in a reciprocating action.

U.S. Pat. No. 2,792,790 to Capps discloses one of the typical air compressors comprising a piston slidably engaged with an inner peripheral surface of a cylinder housing, and a sealing ring engaged between the cylinder housing and the piston, for making an air tight seal between the cylinder housing and the piston. In this typical air compressor, the sealing ring may not effectively make an air tight seal between the cylinder housing and the piston when the piston is tilted relative to the cylinder housing.

For example, U.S. Pat. No. 5,655,887 to Chou discloses another typical air compressor comprising a piston having a conical piston holder pivotally attached thereto, for slidably engaging with the inner peripheral surface of the cylinder housing, and for making an air tight seal between the cylinder housing and the piston. However, the typical air compressors includes a complicated compression mechanism having a base, a compressible conical piston, and a conical piston holder, that may not be easily manufactured and assembled.

U.S. Pat. No. 6,059,542 to Chou discloses a further typical air compressor comprising a piston slidably engaged with an inner peripheral surface of a cylinder housing without a sealing ring. In this typical air compressor, the piston may not be made a suitable air tight seal between the cylinder housing and the piston.

U.S. Pat. No. 6,200,110 to Chou, and U.S. Pat. No. 6,213,725 to Chou disclose two further typical air compressors comprising a piston slidably engaged with an inner peripheral surface of a cylinder housing, and a sealing ring engaged between the cylinder housing and the piston, for making an air tight seal between the cylinder housing and the piston.

In these typical air compressors, the piston is solidly secured to or extended from the piston rod, and will be moved in concert with the piston rod, and thus will be tilted relative to the cylinder housing when the piston rod is rotated or driven by a motor via an eccentric member. However, the sealing ring may be disengaged from the cylinder housing when the piston is moved to bottom or outer end of the cylinder housing, due to tilting or inclined status of the piston rod relative to the cylinder housing, such that the sealing ring may not be used to suitably make an air tight seal between the cylinder housing and the piston.

The present invention has arisen to mitigate and/or obviate the afore-described disadvantages of the conventional pistons for air compressors.

SUMMARY OF THE INVENTION

The primary objective of the present invention is to provide an air compressor including an improved valve device for facilitating a sliding engagement between a piston and a cylinder housing and for effectively controlling the air to flow through the valve device or to flow into and out of the cylinder housing.

In accordance with one aspect of the invention, there is provided an air compressor comprising a cylinder housing including a chamber formed therein, and defined by an inner peripheral surface, a piston slidably received in the chamber of the cylinder housing and having a piston rod extended therefrom, a moving device for moving the piston relative to the cylinder housing in a reciprocating action in order to generate pressurized air, and a sealing ring engaged into the piston and including an outer peripheral channel formed in an upper portion thereof, to form an outer peripheral rib, the outer peripheral rib of the sealing ring being extended out of the piston for slidably engaging with the inner peripheral surface of the cylinder housing and for making an air tight seal between the cylinder housing and the piston even when the piston is tilted relative to the cylinder housing.

The piston includes a base member and an upper cover member engaged onto and located above the base member for retaining the sealing ring between the base member and the upper cover member of the piston. The upper cover member of the piston includes a peripheral flap extended downwardly toward the base member and engaged with the sealing ring for stably retaining the sealing ring in the piston.

The sealing ring includes an inner peripheral channel formed therein for receiving the peripheral flap of the upper cover member and for solidly anchoring the sealing ring to the piston. The base member of the piston includes a peripheral wall extended upwardly therefrom to form an outer peripheral shoulder and an inner compartment therein, the upper cover member of the piston includes a swelling extended downwardly therefrom to engage into the inner compartment of the base member and to anchor the upper cover member to the base member.

The outer peripheral rib of the sealing ring includes an inclined surface for engaging with the inner peripheral surface of the cylinder housing. The outer peripheral rib of the sealing ring includes an upper flat surface formed in an upper portion thereof and formed beside the inclined surface thereof.

The piston includes an air passage formed therein for air flowing purposes, and includes a valve device attached to the piston for selectively blocking the air passage of the piston when the piston is moved relative to the cylinder housing in a compressing stroke, and for selectively opening the air passage of the piston when the piston is moved relative to the cylinder housing in a returning stroke.

The valve device includes a first side secured to the piston and including a second side opposite to the first side thereof, and the piston includes device for limiting the second side of the valve device to move relative to the piston and to prevent the second side of the valve device from being over bent relative to the first side of the valve device.

The limiting device includes an ear extended therefrom and located above the second side of the valve device for engaging with the second side of the valve device and for limiting the second side of the valve device to bend or move relative to the piston. The valve device includes an opening form in the second side thereof, and the limiting device includes a limiting device extended from the piston and extended through the opening of the valve device, and having the ear extended from the limiting device.

The valve device includes an inner peripheral slot formed therein to form a first blade member and a second blade member and to have the inner peripheral slot located between the first blade member and the second blade member. The valve device includes at least one coupling member provided in the second side thereof and coupled between the first blade member and the second blade member, for coupling the first blade member and the second blade member together. The piston includes a bar extended upwardly therefrom for engaging with the valve device and for positioning and for anchoring the valve device.

A supporting plate may further be provided to support the cylinder housing, the cylinder housing includes an outlet tube having a compartment formed therein and communicating with the chamber of the cylinder housing for receiving pressurized air from the chamber of the cylinder housing, and includes a valve seat provided in the outlet tube and located between the outlet tube and the cylinder housing, and a spring-biased check valve is disposed in the outlet tube and engaged with the valve seat, to prevent the pressurized air from flowing backwardly from the compartment of the outlet tube into the chamber of the cylinder housing inadvertently.

The moving device includes a motor attached to the plate and having a spindle extended through the plate, and an eccentric member coupled to the spindle and having a pin coupled to the piston rod, to move the piston relative to the cylinder housing. The plate may include a gear rotatably attached thereto and having a space formed by a peripheral casing to receive the eccentric member.

The cylinder housing includes a first duct, a second duct, and at least one third duct extended outwardly from the outlet tube and communicating with the compartment of the outlet tube, for receiving the pressurized air from the outlet tube, a pressure gauge attached to the first duct, a nozzle coupled to the second duct and a relief valve may be attached to the third duct for relieving the pressure in the outlet tube.

Further objectives and advantages of the present invention will become apparent from a careful reading of the detailed description provided hereinbelow, with appropriate reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an air compressor in accordance with the present invention;

FIG. 2 is a partial cross sectional view of the air compressor, taken along lines 2-2 of FIG. 1;

FIG. 3 is another partial cross sectional view similar to FIG. 2, illustrating the operation of the air compressor;

FIG. 4 is a partial exploded view illustrating the piston and the valve member of the air compressor;

FIG. 5 is a perspective view illustrating the piston and the valve member of the air compressor;

FIG. 6 is a cross sectional view of the air compressor taken along lines 6-6 of FIG. 5;

FIG. 7 is a cross sectional view similar to FIG. 2, illustrating the operation of the air compressor;

FIG. 8 is an enlarged partial cross sectional view illustrating the improved sealing ring for the air compressor;

FIG. 9 is an enlarged plan schematic view illustrating the operation of the improved sealing ring of the air compressor;

FIG. 10 is another enlarged plan schematic view similar to FIG. 9, illustrating the further operation of the improved sealing ring of the air compressor; and

FIG. 11 is a partial exploded view similar to FIG. 4, illustrating the other arrangement of the piston and the valve member of the air compressor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings, and initially to FIGS. 1-3, an air compressor in accordance with the present invention comprises a supporting base 10 including a plate 11 and a cylinder housing 12 provided on or extended from the plate 11 and preferably formed integral with the plate 11. The cylinder housing 12 includes a chamber 13 formed therein (FIGS. 2, 3) for slidably receiving a piston 30 therein, and includes one or more fins 14 extended laterally or radially outwardly therefrom (FIG. 1), for such as heat dissipating purposes. The piston 30 includes an extension or piston rod 31 extended therefrom, and is slidable in reciprocating action in the chamber 13 of the cylinder housing 12 for generating pressurized air.

The cylinder housing 12 includes an outlet tube 15 extended upwardly or outwardly from the top thereof, and having a compartment 16 formed therein and communicating with the chamber 13 of the cylinder housing 12, for receiving the pressurized air from the chamber 13 of the cylinder housing 12. A spring-biased check valve 17 (FIGS. 2, 3) may be disposed in the outlet tube 15, and engaged with a valve seat 18 that is formed or provided between the outlet tube 15 and the cylinder housing 12. A relief valve or safety valve (not shown) or the like may further be provided and attached to the outlet tube 15, for relieving the pressurized air when the air pressure within the cylinder housing 12 and the outlet tube 15.

The spring-biased check valve 17 may thus be used to limit the pressurized air to flow from the chamber 13 of the cylinder housing 12 into the compartment 16 of the outlet tube 15 only, and to prevent the pressurized air from flowing backwardly from the compartment 16 of the outlet tube 15 into the chamber 13 of the cylinder housing 12. A cap 19 may be attached to the outer or free end of the outlet tube 15 with such as threading engagements, for blocking or enclosing the compartment 16 of the outlet tube 15, and for stably retaining the spring-biased check valve 17 within the compartment 16 of the outlet tube 15.

The cylinder housing 12 further includes one or more ducts 20, 21, 22, 23 extended outwardly from the outlet tube 15, and communicating with the compartment 16 of the outlet tube 15, for receiving the pressurized air from the compartment 16 of the outlet tube 15. The ducts 20, 21, 22, 23 may be coupled to various kinds of facilities that require pressurized air supplied thereto. For example, a relief valve 24 may be provided and attached to one of the ducts 20 for relieving the pressurized air when the air pressure within the cylinder housing 12 and/or the outlet tube 15 is over a predetermined pressure, and thus for preventing the cylinder housing 12 and/or the outlet tube 15 from being over-pressurized and damaged.

A pressure gauge 25 may be provided and attached to the other duct 21 for detecting and showing the air pressure within the cylinder housing 12 and/or the outlet tube 15. A nozzle 26 may be provided and attached to another duct 22, for allowing the pressurized air to be supplied from the chamber 13 of the cylinder housing 12 and the compartment 16 of the outlet tube 15 to various facilities that require pressurized air supplied thereto, with the nozzle 26.

It is to be noted that the provision or the extension of the ducts 20, 21, 22, 23 from the outlet tube 15 allows the relief valve 24 and the pressure gauge 25 and the nozzle 26 to be easily and readily attached to or coupled to the outlet tube 15 with the ducts 20, 21, 22, 23, without additional or specialized coupling members or tools. One or more lids (not shown) may further be provided and attached or secured to either of the ducts 20, 21, 22, 23 with such as threading engagements, for selectively enclosing or blocking the ducts 20, 21, 22, 23, when the ducts 20, 21, 22, 23 are not required to be used.

A gear 40 is rotatably attached to the lower portion of the plate 11 with one or more bearings (not shown) and a shaft 41, and includes a space 43 formed therein and defined by a peripheral casing 44 for receiving and securing an eccentric member 45 therein (FIGS. 1, 2). The eccentric member 45 may be secured to the gear 40 with such as fasteners (not shown) and may thus be rotated in concert with the gear 40, and includes a crank or an eccentric pin 47 extended therefrom and coupled to the piston rod 31 of the piston 30, in order to actuate or to move the piston 30 relative to the cylinder housing 12 in reciprocating actions.

A motor 50 may be attached or secured to the upper portion 15 of the plate 11 with such as fasteners (not shown), and includes a spindle 52 extended through the plate 11 (FIG. 2), and includes a pinion 53 secured to the spindle 52 thereof, and engaged with the gear 40, for allowing the gear 40 to be rotated or driven by the motor 50 via the pinion 53, and thus for allowing the piston 30 to be actuated or moved relative to the cylinder housing 12 in reciprocating actions by the eccentric member 45 and the eccentric pin 47. A fan device 54 may further be provided and coupled to the motor 50 for being rotated or driven by the motor 50 to generate circulating or ventilating air.

In operation, as shown in FIGS. 2 and 3, the piston 30 may be actuated or moved relative to the cylinder housing 12 in reciprocating actions by the motor 50 via pinion 53, the gear 40, the eccentric member 45 and the eccentric pin 47, in order to generate a pressurized air, and to allow the pressurized air to flow into the outlet tube 15, and then to flow out through either or all of the ducts 20, 21, 22, 23, and thus to allow the air pressure within the cylinder housing 12 and/or the outlet tube 15 to be detected and shown by the pressure gauge 25, and to allow the pressurized air to be supplied into the facilities that require pressurized air supplied thereto, with the nozzle 26, and/or to allow the pressurized air to be relieved via the relief valve 24 when the cylinder housing 12 and/or the outlet tube 15 is over-pressurized.

As shown in FIGS. 4-8, the piston 30 includes an air passage 32 formed therein and arranged for allowing the air to flow through the air passage 32 of the piston 30. A spring blade or valve device 60 includes one or first side 61 attached or secured to one or first side 34 of the piston 30 with one or more fasteners 62, and includes a suitable resilience for biasing to block or enclose the air passage 32 of the piston 30 and for controlling the air to flow through the air passage 32 of the piston 30. The above described structure is typical and will not be described in further details.

The valve device 60 further includes an orifice 63 formed in the one or the first side 61 thereof (FIG. 4), for receiving a peg 33 that is extended upwardly from the piston 30 and for anchoring or positioning the valve device 60 to the piston 30, and includes an opening 64 form in the second side 65 of the valve device 60 and located opposite to or distal to the opening 63 of the valve device 60. The valve device 60 is made of resilient metal or steel materials and may be forced to be bent relative to the piston 30 in order to block and to selectively open the air passage 32 of the piston 30 and to allow the air to flow through the piston 30 at one time when the air passage 32 of the piston 30 is partially opened by the spring blade or valve device 60.

The piston 30 includes a bar 35 extended upwardly from the first side 34 of the piston 30 for engaging with and for positioning and/or anchoring the valve device 60, and further includes a limiting means or device 37 extended upwardly from the second side 38 of the piston 30 and located opposite to the bar 35, and preferably arranged to have the air passage 32 of the piston 30 formed and located between the bar 35 and the limiting means or device 37. The limiting device 37 is extended through the opening 64 of the valve device 60 (FIGS. 5-7).

The limiting device 37 includes an extension or ear 39 extended therefrom and extended or faced away from the bar 35, and preferably parallel to the upper surface of the piston 30, and extended and located above the second side 65 of the valve device 60 for engaging with the second side 65 of the valve device 60, and thus for limiting the second side 65 of the valve device 60 to bend or to move relative to the piston 30, and for preventing the second side 65 of the valve device 60 from being over bent or deformed relative to the first side 61 of the valve device 60.

Alternatively, the limiting device 37 may be extended and located outside the valve device 60 without engaging through the opening 64 of the valve device 60, and the extension or ear 39 may also be extended inwardly of the valve device 60 and located above the second side 65 of the valve device 60 for engaging with the second side 65 of the valve device 60 and for limiting the second side 65 of the valve device 60 to bend or to move relative to the piston 30, and thus for preventing the second side 65 of the valve device 60 from being over bent or deformed relative to the first side 61 of the valve device 60.

The valve device 60 further includes an inner peripheral slot 66 formed therein, for forming an outer peripheral blade member or first blade member 67 and an inner spring blade or second blade member 68 therein, and for allowing the inner peripheral slot 66 thereof to be located between the first blade member 67 and the second blade member 68. The inner or second blade member 68 includes an area greater than that of the air passage 32 of the piston 30 for biasing and blocking the air passage 32 of the piston 30 and for controlling the air to flow through the air passage 32 of the piston 30.

The valve device 60 further includes one or more, such as two coupling members 69 formed or provided in the other or the second side 65 thereof, and coupled between the first blade member 67 and the second blade member 68, for coupling the first blade member 67 and the second blade member 68 together, and for increasing the resilience or moving stroke of the second blade member 68. Alternatively, as shown in FIG. 11, the valve device 60 may include no inner peripheral slot formed therein and no outer peripheral blade member or first blade member and no inner spring blade or second blade member formed therein, and the valve device 60 may also be used to block and to selectively open the air passage 32 of the piston 30.

In operation, as shown in FIGS. 5-7, the other or the second side 65 of the first blade member 67 or of the valve device 60 may be moved or sprung away from the upper surface of the piston 30, and the second blade member 68 of the valve device 60 may further be moved or sprung away from the first blade member 67 or of the valve device 60, for allowing the second blade member 68 of the valve device 60 to have a better movability or resilience to be moved or sprung away from the upper surface of the piston 30, in order to suitably and selectively engage with the piston 30, and so as to openably and selectively block the air passage 32 of the piston 30, and so as to effectively control the air to flow through the air passage 32 of the piston 30. The improved valve device 60 has been disclosed and filed in a co-pending US application.

As shown in FIGS. 4-8, the piston 30 preferably includes a base member 70 having a peripheral wall 71 extended upwardly therefrom to form an outer peripheral shoulder 72 and an inner compartment 73 therein which is communicating with the air passage 32 of the piston 30, and the piston 30 includes an upper cover member 75 engaged onto and located above the base member 70 and having a swelling 76 extended downwardly therefrom to engage into the inner compartment 73 of the base member 70, and secured to the base member 70 with such as adhesive materials, force-fitted engagements, fasteners or latches (not shown), or by welding processes, or the like. Alternatively, the upper cover member 75 and the base member 70 may also be formed integral with each other.

The upper cover member 75 may include the peg 33, the bar 35 and the limiting device 37 extended therefrom, and the air passage 32 of the piston 30 may be formed through both the upper cover member 75 and the base member 70 for allowing the air to flow through the air passage 32 and both the upper cover member 75 and the base member 70 of the piston 30. The upper cover member 75 may further include a peripheral flap 77 formed and provided around the swelling 76 (FIGS. 6-10) and extended downwardly toward the base member 70, for such as positioning and anchoring a sealing ring 80 which will be discussed hereinafter.

The sealing ring 80 is engaged onto or around the peripheral wall 71 of the base member 70 of the piston 30 and engaged with the outer peripheral shoulder 72 of the base member 70 of the piston 30, to allow the sealing ring 80 to be stably anchored and retained between the upper cover member 75 and the base member 70 of the piston 30. It is preferable that the sealing ring 80 includes an inner peripheral channel 81 and an outer peripheral channel 82 formed in the upper portion thereof, to form or define an inner peripheral rib 83 and a middle peripheral rib 84 and an outer peripheral rib 85, in which the peripheral flap 77 of the upper cover member 75 is engaged into the inner peripheral channel 81 of the sealing ring 80 for solidly anchoring and retaining the sealing ring 80 to the piston 30.

The outer peripheral rib 85 is thus freely extended upwardly and outwardly from the outer peripheral portion of the sealing ring 80 for slightly extending out of the outer peripheral portion of the piston 30 and for resiliently and effectively engaging with the inner peripheral surface 90 of the cylinder housing 12 (FIGS. 2, 3, 9, 10). It is preferable that the outer peripheral rib 85 of the sealing ring 80 includes a flat surface 86 formed in the upper portion thereof and preferably parallel to the bottom surface 87 of the sealing ring 80 (FIG. 8), and further includes an inclined surface 88 formed in the upper and outer portion thereof and formed beside or adjacent to the flat surface 86 thereof.

In operation, as shown in FIGS. 9-10, when the piston 30 is forced to move or to slide in the cylinder housing 12 in reciprocating action, by the motor 50 and the pinion 53 and the gear 40 and the eccentric pin 47, the piston 30 may be slightly inclined or tilted relative to the cylinder housing 12. The outer peripheral rib 85 that is slightly extended out of the piston 30 may be slidably engaged with the inner peripheral surface 90 of the cylinder housing 12 to make a suitable air tight seal between the piston 30 and the cylinder housing 12 even when the piston 30 is inclined or tilted relative to the cylinder housing 12.

Accordingly, the air compressor in accordance with the present invention includes an improved valve device for effectively controlling the air to flow through the valve device or to flow into and out of the cylinder housing.

Although this invention has been described with a certain degree of particularity, it is to be understood that the present disclosure has been made by way of example only and that numerous changes in the detailed construction and the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention as hereinafter claimed. 

1. An air compressor comprising: a cylinder housing including a chamber formed therein, and defined by an inner peripheral surface, a piston slidably received in said chamber of said cylinder housing and having a piston rod extended therefrom, means for moving said piston relative to said cylinder housing in a reciprocating action in order to generate pressurized air, and a sealing ring engaged into said piston and including an outer peripheral channel formed in an upper portion thereof, to form an outer peripheral rib, said outer peripheral rib of said sealing ring being extended out of said piston for slidably engaging with said inner peripheral surface of said cylinder housing and for making an air tight seal between said cylinder housing and said piston even when said piston is tilted relative to said cylinder housing.
 2. The air compressor as claimed in claim 1, wherein said piston includes a base member and an upper cover member engaged onto and located above said base member for retaining said sealing ring between said base member and said upper cover member of said piston.
 3. The air compressor as claimed in claim 2, wherein said upper cover member of said piston includes a peripheral flap extended toward said base member and engaged with said sealing ring for stably retaining said sealing ring in said piston.
 4. The air compressor as claimed in claim 3, wherein said sealing ring includes an inner peripheral channel formed therein for receiving said peripheral flap of said upper cover member and for solidly anchoring said sealing ring to said piston.
 5. The air compressor as claimed in claim 2, wherein said base member of said piston includes a peripheral wall extended upwardly therefrom to form an outer peripheral shoulder and an inner compartment therein, said upper cover member of said piston includes a swelling extended downwardly therefrom to engage into said inner compartment of said base member and to anchor said upper cover member to said base member.
 6. The air compressor as claimed in claim 1, wherein said outer peripheral rib of said sealing ring includes an inclined surface for engaging with said inner peripheral surface of said cylinder housing.
 7. The air compressor as claimed in claim 6, wherein said outer peripheral rib of said sealing ring includes an upper flat surface formed in an upper portion thereof and formed beside said inclined surface thereof.
 8. The air compressor as claimed in claim 1, wherein said piston includes an air passage formed therein for air flowing purposes, and includes a valve device attached to said piston for selectively blocking said air passage of said piston when said piston is moved relative to said cylinder housing in a compressing stroke, and for opening said air passage of said piston when said piston is moved relative to said cylinder housing in a returning stroke.
 9. The air compressor as claimed in claim 8, wherein said valve device includes a first side secured to said piston and including a second side opposite to said first side thereof, and said piston includes means for limiting said second side of said valve device to move relative to said piston and to prevent said second side of said valve device from being over bent relative to said first side of said valve device.
 10. The air compressor as claimed in claim 9, wherein said limiting means includes an ear extended therefrom and located above said second side of said valve device for engaging with said second side of said valve device and for limiting said second side of said valve device to bend or move relative to said piston.
 11. The air compressor as claimed in claim 10, wherein said valve device includes an opening form in said second side thereof, and said limiting means includes a limiting device extended from said piston and extended through said opening of said valve device, and having said ear extended from said limiting device.
 12. The air compressor as claimed in claim 8, wherein said valve device includes an inner peripheral slot formed therein to form a first blade member and a second blade member and to have said inner peripheral slot located between said first blade member and said second blade member.
 13. The air compressor as claimed in claim 12, wherein said valve device includes at least one coupling member provided in said second side thereof and coupled between said first blade member and said second blade member, for coupling said first blade member and said second blade member together.
 14. The air compressor as claimed in claim 8, wherein said piston includes a bar extended upwardly therefrom for engaging with said valve device and for positioning and for anchoring said valve device.
 15. The air compressor as claimed in claim 1 further comprising a supporting plate to support said cylinder housing, said cylinder housing including an outlet tube having a compartment formed therein and communicating with said chamber of said cylinder housing for receiving pressurized air from said chamber of said cylinder housing, and including a valve seat provided in said outlet tube and located between said outlet tube and said cylinder housing, and a spring-biased check valve disposed in said outlet tube and engaged with said valve seat, to prevent the pressurized air from flowing backwardly from said compartment of said outlet tube into said chamber of said cylinder housing.
 16. The air compressor as claimed in claim 15, wherein said moving means includes a motor attached to said plate and having a spindle extended through said plate, and an eccentric member coupled to said spindle and having a pin coupled to said piston rod, to move said piston relative to said cylinder housing.
 17. The air compressor as claimed in claim 16, wherein said plate includes a gear rotatably attached thereto and having a space formed by a peripheral casing to receive said eccentric member.
 18. The air compressor as claimed in claim 1, wherein said cylinder housing includes a first duct, a second duct, and at least one third duct extended outwardly from said outlet tube and communicating with said compartment of said outlet tube, for receiving the pressurized air from said outlet tube, a pressure gauge attached to said first duct, a nozzle coupled to said second duct. 